關鍵字: 乳酸菌、酯酶、玉米赤黴烯酮、降解 。
Esterase can break the ester linkage of Zearalenone (ZEA) structure and lead to ZEA inactivation. Previous studies indicated that the yeast that expressed albusin B (a bacteriocin from rumen cellulolytic bacterium Ruminococcus albus 7) could stimulate the proliferation of intestinal lactic acid bacteria (LAB). Furthermore, the yeast cell wall also showed good ZEA absorption ability. This study attempted to development a mixed type probiotic feed additive with ZEA degradation activity through selecting high esterase activity LAB that compatible with albusin B. The probiotic growth tested result indicated that addition of bacteriocin (0.01-0.1 mg/mL) enhanced all test bacteria (Lactobacillus acidophilus、Bifidobacterium and Lb. casei) growth about 2 to 3 times. To select LAB strains with esterase activity that compatible with albusin B, LAB strains collected from digestive tract content or faces from mammal and poultry were selected by MRS broth with 0.25% albusin B and added 2% Tween 20 as carbon source. Ten selected LAB strains with high esterase activity were cultured in MRS broth with ZEA for ZEA degradation activity test. The ZEA degradation test results indicated that no toxic ZEA metabolites like α- or β-zearalenone were shown in LAB degradation product, it suggested that the detoxification mechanism of selected LAB might depend did break the ZEA structure. Three LAB strains with the highest ZEA degradation ability were selected and identified as Lactobacillus plantarum by API CHL 50kit. The supernatant and cell pellet of identified LAB strains were applied to test the degradation ability of ZEA individually. The HPLC assay result indicated that 3 strains (strains B1 and B2 from bats faces, strain D10 from ducks ileum) showed the highest ZEA treatment ability at bacteria concentrations about 109 CFU/mL. The higher ZEA degradation ability of LAB culture supernatant was found between 6-8 hours after incubation as the cell count over 109 CFU/mL and degradation ability increased as esterase activity increased. The pellet of LAB strain D10 showed 49% absorption ability for ZEA, and its incubation supernatant showed 31% degradation ability for ZEA at pH 6. When reaction condition adjusted to pH 8, the B2 strain showed 37% degradation ability for ZEA. The bile salt and acid tolerant test result indicated that all selected LAB strains had high tolerance to acid and 0.3% bile salt. Three LAB strains (strains B1 and B2 from bats faces, strain D10 from ducks ileum) had excellence degradation and high tolerance to acid and 0.3% bile salt.The selected LAB strain with high ZEA degradation could combination with yeast expressed albusin B as a mixed type probiotic ZEA degradation feed additive.
